31 May 2006

I use the various free translation programs available on the Internet frequently to translate mostly taxonomic texts from German (and sometimes French) to English. How can one test the accuracy of such a program?

I am starting with the assumption that a relatively simple sentence should retain its original meaning, or a meaning close to its original meaning, no matter how many times it is translated successively, if each translation is accurate.

So, here is a test using two programs.

Original:

1. Don't forget to take a picture of the baby snail before the sun sets behind the limestone peak.

5. Do not forget to take an image to the baby's limaza before the valuations of the sun behind the top part of limestone.

Obviously, we end up with a meaningless sentence. One problem is Google’s translation of "Baby-Schnecke" to French as "la limace de bébé", which means "baby’s slug". The French word for snail is actually escargot. And then, when #3 is translated into Spanish, "limace" becomes "limaza", although the latter word is not in the Spanish dictionary. (The Spanish word for snail is caracol.)

The second problem is "before the sun sets" turns into "before the valuations of the sun", also during Google’s translation of #2 to French.

Here’s another trial starting with the same English sentence, but this time doing all the translations with Babel Fish.

5b. They do not forget to make a photography to the slimy one of baby, before the sun fits the part of limestone behind.

This time we end up with even a worse result. Once again, the German word for snail, Schnecke is translated to French as limace.

To get around the limitations of these programs, when I am translating a text, I usually use Promt and Google, compare the translations with each other and then pick the best sentences to create one edited translation. Of course, some knowledge of the subject matter and familiarity with the original language both help.

30 May 2006

The genus Discus is one of the land snail genera with representatives both in Europe and North America. There are several species of Discus in North America and 3 in Europe, including D. rotundatus that has been introduced to many countries, including the U.S.

The snail pictured here, D. patulus, is endemic to the U.S. This specimen, whose shell was 8.5 mm in diameter, came from Garrett Co., Maryland.

Thomas Say described this species as Helix perspectiva in 1817 in one of his first papers on snails (Journal of the Academy of Natural Sciences of Philadelphia, vol. 1, p. 18). However, unbeknown to Say, the specific name perspectiva had already been used for another species. So, the name given to it, Helix patula, by Deshayes in 1830 replaced Say's H. perspectiva.

As Say indicated in his description (above), his specimen(s) had been collected by his friend the French naturalist and painter Charles Alexandre Lesueur (1778-1846). Lesueur lived in the U.S. between 1815 and 1837. He was a member of the Academy of Natural Sciences of Philadelphia and later moved to New Harmony, Indiana with Say and others to participate in Richard Owen's short-lived experimental utopian society. Say's wife Lucy took drawing and painting classes from Lesueur in Philadelphia and New Harmony.

According to Say's biographer Stroud (Thomas Say: new world naturalist. 1992), when Lesueur first came to the U.S. he spoke little English. Say read his papers at the Academy's meetings and prepared them for publication in the Academy's journal. In return, Lesueur helped Say with his French and drew illustrations for his articles.

29 May 2006

Take me back to ConstantinopleNo, you can't go back to ConstantinopleNow it's Istanbul, not ConstantinopleIstanbul (Not Constantinople), first recorded by The Four Lads in 1953

On this day in 1453, the Ottomans, under the command of Sultan Mehmet II, took Constantinople, ending the more than 1100 year-old Byzantine Empire.

The name Constantinople ("City of Constantine") comes from the name of the Byzantine emperor Constantine, who around 330 A.D. rebuilt the earlier city of Byzantium.

This mosaic from Haghia Sophia, built around 532 A.D. by the emperor Justinian in Constantinople shows the emperors Justinian (left) and Constantine (right) presenting to the Virgin Mary what appear to be models of Haghia Sophia and the city, respectively. Almost immediately after the city fell, the Ottomans converted Haghia Sophia to a mosque, but rather than destroy its mosaics, they plastered over them. Haghia Sophia, with its mosaics restored, is now a museum. This picture is from a slide I took in 1987.

To its residents, Constantinople was the city without a need to further specify. Thus, the best explanation for the obscure origin of its present name Istanbul, which actually has no meaning in Turkish, is the Greek phrase Ης την Πόλη (Is tin Poli = "to the city"). It is believed that the Ottoman Turks, upon repeatedly hearing that phrase, started using it as a name.

This is supported by what appears to be a similar derivation: Istanköy, the Turkish name of the Greek island of Kos. (Köy means village, but istan is meaningless.)

However, Constantinople didn't become Istanbul right after its fall. It had many other names throughout the Ottoman centuries, including Dersaadet (used until the early 20th century), Islambol ("Plenty of Islam", obviously a derivation from the meaningless Istanbul) and Kostantiniye, "City of Kostantin" from Arabic.

Sultan Mehmet II, a.k.a. Mehmet the Conqueror, in a painting attributed to the Venetian painter Gentile Bellini (1429-1507). The original is in the National Gallery in London, England. For a discussion of this painting in a historical context, read this Guardian article.

Note: To properly view the Greek characters, set the encoding of your browser to Unicode, UTF-8. If you are using another browser, read the comments to this post.

26 May 2006

I have had 2 live P. elegans for almost 2 years, but only recently started paying close attention to them. Here are a series of photographs of how they come out of their shells.

As explained in the previous post about this species, when the snail is completely withdrawn into its shell, its aperture is sealed with a hard, calcareous operculum that is permanently attached to the top of the snail's foot. In A, the operculum is starting to lift up. In B, the red arrow points at the tip of one of the tentacles that is "peeking" out. Unlike most other land snails, the eyes of P. elegans are not at the tips of its tentacles. However, there must be some chemical receptors on the tentacles, perhaps in the darker tips, that the snail seems to be using to check out the outside world before any other part of the body is brought out. Right below the tentacle, you may also notice the tip of the proboscis (it is easily visible in the original high resolution picture). In C, both tentacles and the proboscis are out. Notice that each tentacle is pointing in a different direction, which, again, seems to suggest that the snail is using them to sense the surroundings.

In B and C, the deeply furrowed part to the other side of which the operculum is attached is actually the sole of the foot. In D, the snail has twisted its foot around and is bringing the sole in contact with the ground. The head has also twisted around and is momentarily facing the ground. In E, most of the sole is resting on the ground, the left eye is visible at the base of the left tentacle, but the shell hasn't moved to its proper position yet. Finally, in G, the snail has twisted its shell around to its "cruising" position on top of the operculum. The proboscis in contact with the ground is visible in the front. The snail is ready to push the pedal to the metal!

This seemingly complex set of maneuvers, which is reversed when the snail is withdrawing into its shell, is necessary to protect the head, the most vital part of the snail's body that is exposed to the outside. When a snail senses danger, it withdraws its head into its shell first, followed by the rest of the foot. But, the problem is that before the snail can come back out, it needs to put its tentacles out to determine if it's safe to come out. The snail accomplishes that by doubling over itself within its shell. Another reason why the snail's head needs to be located near the aperture, even though it goes in before the foot, is that the lung and its opening are located in the head.

In this case, unintelligent evolution couldn't come up with a better solution other than turning the snails into contortionists.

Interestingly, the land snails that have lost their opercula during evolution go thru the same sequence when they are withdrawing or coming out of their shells.

25 May 2006

"It is a while ago now, but I vividly remember talking with some British friends here in Athens who are both married to Greek women.

They were all about to fly to Istanbul for a long weekend away... fun, interesting but nothing particularly remarkable.

Unless you are Greek.

Their wives both highly educated and well-travelled were distinctly apprehensive.

For them this would mean crossing a thin red-line and entering the camp of the old enemy.

They would be constantly looking over their shoulders as they wandered through the crowded, chaotic streets of the once-fabled capital of the Ottoman empire."

No, Mr. Galpin, they wouldn’t be constantly looking over their shoulders. Because, nobody would know they were Greek and even if they did, nobody would care they were Greek.

Do you know, Mr. Galpin, that Greeks have always lived in Istanbul? Do you know that even after the Ottomans took Constantinople in 1453, the surviving Greek population stayed, they weren’t forced to leave, because the Ottomans didn’t care?

Do you know, Mr. Galpin, that there are several thousand Greeks (strictly speaking, Turkish citizens of Greek ancestry) living peacefully in Istanbul? Take a look at the picture on this page, Mr. Galpin. Does it look like those people are looking over their shoulders in fear?

Yes, there have been some politically motivated unfortunate incidents in Istanbul mostly in the 1950s. But, no, Mr. Galpin, Greeks visiting Istanbul or any other place in Turkey for that matter, should have nothing to fear now (even after the latest incident over the Aegean), except perhaps their own fear of Turks.

To improve the Turkish-Greek relations, we need more intermingling of the populations, of the common people, of those who were forced to leave their homelands after the Lausanne Treaty of 1923 (see here and here).

What we don’t need is more of this sort of journalistic nonsense. I suggest, Mr. Galpin, that next time you are writing something along these lines, use some common sense and gather some reliable information beforehand so that you will at least sound a little bit more intelligent.

23 May 2006

You have 2 identical cubic boxes. You completely fill (without going above the top) one of them with iron spheres and the other one with iron cubes. The length of an inner edge of each box is an exact multiple of one edge of a cube and of the diameter of a sphere.

1. Which box will have more items (cubes or spheres) in it?2. Which filled box will have a smaller density?

(Modified from a question in Ebbing & Gammon, General Chemistry, 6th ed., 1999.)

22 May 2006

Can all terrestrial snails repair their shells? The ability to repair a damaged shell is such a vital requirement that it would be expected to have evolved in all land snails. Since marine snails are known to be able to repair their shells and terrestrial snails have descended from marine ancestors, it is perhaps more accurate to say that none of the terrestrial snail lineages would be expected to have lost their ancestors' ability to repair damaged shells.

Nevertheless, building and repairing a shell is costly and time consuming. Thus, some snail species may have traded off the shell repair ability with rapid growth and abundant egg production.

There are 2 ways to determine if a given snail species can repair damaged shells. First, one may examine shells for scars of repaired damages. I have presented examples of repaired shells here and here. Also check out this paper of mine to see how I used this method to establish that Pomatias elegans can repair its shell. Of course, the lack of scars in a particular collection of shells doesn’t necessarily mean that the snails can’t repair their shells.

Second, if live snails are available and can be kept in captivity in good health, one may remove sections of their shells and then monitor the snails to see if they will repair the breaks. However, the interpretation of the results from such an experiment is not straightforward. A snail that can repair its shell in captivity may not be able to do so in the wild, or vice versa.

I have been cataloging all major scars I come across on land snail shells. My purpose is to determine if there are indeed any species or higher groups that have lost the ability to repair their shells. Here is a picture of a Cerion shell with a scar that is about half a whorl long (arrows).

21 May 2006

Here is a good dark ale with a rather mild taste and a nice aroma. Is it nutty? Perhaps. I suppose all good things in life are a bit nutty.

There are many "nut brown ales" out there. The origin of this particular type of beer is from England; Samuel Smith's Nut Brown Ale perhaps being the best known of them all.

Wild Goose Nut Brown Ale is brewed by the Frederick Brewing Company in Frederick, Maryland, not too far from where I live. Unfortunately, the company's website is one of those sites with almost no tangible information about their beers or anything else.

19 May 2006

The majority of snail shells are normally dextral (the coiling of the shell is right-handed). This means that when the shell is held with its aperture facing the observer and its apex pointing up, the aperture will be on the right. Occasionally, one may chance upon a freak individual whose shell is coiled in a direction opposite to that of its conspecifics. The Helix aspersa shell shown here, from the Smithsonian's National Museum of Natural History, is one such example.

17 May 2006

"When one looks carefully at a biological problem, one can usually discover more than one casual explanation...Indeed, it is quite possible that in biology the majority of phenomena and processes must be explained by a plurality of theories."

Ernst Mayr This is Biology (1997)

One long standing controversy in evolutionary biology is about the respective contributions sympatry and allopatry have made during the origins of the millions of species that now exist.

A new species (or 2 new species) can develop if gene flow between 2 populations ceases or slows down to permit the independent evolution of the 2 populations.

Allopatric (or geographic) speciation takes place when 2 populations are geographically isolated from each other by, for example, a mountain chain, or an ocean. Because the members of the 2 populations cannot mate and exchange genes with each other, the populations may start to diverge genetically and phenotypically and eventually end up being 2 separate species. In extreme cases of allopatry, there will be no gene flow between the diverging populations.

The opposite of this is sympatric speciation, which takes place in 2 populations whose distribution ranges are largely overlapping. Individuals initially belonging to the same species may begin to differentiate from each other when they start eating different foods or living in different habitats. If the slight genetic differences that may exist between such individuals are reinforced by assortive mating1, 2 populations may emerge and begin to diverge genetically and phenotypically to eventually become separate species. New species may originate even when there is some gene flow between the 2 populations.

An intermediate mechanism is parapatric speciation, which takes place in contiguous, but otherwise geographically isolated (allopatric) populations.

Diagrammatic representation of population divergence in allopatric and sympatric speciation. The vertical axis represents time, running from older, below, to younger, above. The circles and crosses represent the different genotypes. Darkening of the symbols symbolize new species. Modified from a drawing in G.G. Simpson. 1983. Fossils and the History of Life. Scientific American Books.

The late Ernst Mayr was a strong proponent of allopatric speciation and for most of his long career, he discounted sympatric speciation as a viable mechanism. However, an increasing number of studies have been demonstrating that sympatric speciation is possible and may have taken place more often than traditionally believed.

A well-written short essay by Chris D. Jiggins2 in the 9 May issue of Current Biology reviews some recent studies and presents a good argument in favor of sympatric speciation, while pointing out that the usual division of speciation events along a strict line as either sympatric or allopatric creates an “artificial dichotomy”. In line with Mayr’s opinion about the necessity to explain biological processes by more than one theory, Jiggins suggests that in most cases of speciation, sympatric and allopatric processes may both have been reponsible.

"…allopatric and sympatric speciation lie at the opposite ends of a continuum, which runs from zero to maximal gene flow between diverging populations. These new studies provide good evidence that fully sympatric speciation can occur, but most examples probably lie somewhere in between these two extremes."

As is usually the case with any genuine scientific controversy, this one will continue to inspire further research and lead to better understandings of the many-faceted speciation events in nature. Jiggins ends his paper by laying out potential paths for future research.

"…we should abandon the common assumption that allopatric speciation is the ‘null hypothesis’ with all the burden of proof lying on the hypothesis of speciation with gene flow. Instead, speciation research should concentrate on the more proximal causes of speciation, rather than intractable questions of geography. Key questions that we can answer include whether speciation results from natural selection and/or genetic drift, and what traits and genetic architectures are causal in divergence."

1. The mating of individuals preferentially with others of their own genotype is called assortive mating. The opposite of assortive mating is random mating.2. Chris D. Jiggins. Sympatric Speciation: Why the Controversy? Current Biology, Vol 16, R333-R334, 09 May 2006.

16 May 2006

I found this today out in the open under a tree. Is it an Eastern Bluebird egg? I know robin eggs are darker blue. In any case, it is all over for whatever is inside; it won't be in next year's mate selection games.

15 May 2006

I only collect the dead butterflies I come across. This was a "roadkill" from last summer. Since then it had become quite dry and fragile. When I was handling it yesterday, it started to fall apart. Luckily, what was left behind was enough to identify it (if I am not mistaken) as a Common Buckeye.

The "eye" above is the one marked with an arrow in the first picture. It was about 4 mm across. Once I flattened under a glass plate, it became a good target to test my set-up for "extreme" close-up photography. The picture below is an enlargement of the purplish scales near the center of the eye. Each of those scales was about 53 micrometers wide.

Technical info: The wing was photographed with an Olympus E-500 with a Zuiko 35 mm macro lens plus an EX-25 extension tube. The camera was mounted vertically as shown here. I used two 1-watt L.E.D. lights positioned across from each other, saved the pictures in RAW format and corrected the slight shift in color towards blue by specifying a gray point as explained here. Focus was adjusted manually (auto focus doesn't work with the extension tube). At ISO 200 exposure was 1/25 s at f5.6 with a 3-second mirror lock.

14 May 2006

This snail differs from the more familiar pulmonate land snails in having an operculum that closes the aperture of the shell when the snail is completely withdrawn into its shell.

Two additional characteristics of this snail that distinguish it from pulmonate snails are its one pair of tentacles (as opposed to 2 in pulmonates) and its eyes at the bases of its tentacles (as opposed to the location of the eyes at the tips of the tentacles in pulmonates). In these and many other anatomical respects, Pomatias elegans is more similar and evolutionarily closer to marine gastropods than it is to pulmonate land snails.

Note the left eye visible at the base of the left tentacle. Also note how the shell rests on the operculum when the snail is crawling.

The distribution range of P. elegans extends from an isolated spot in western Ireland thru southern England and most of central Europe all the way to Istanbul in Turkey. The colonies of P. elegans in the Istanbul area appear to be at the easternmost limit of the range of this species1.

12 May 2006

Eastern Tailed-Blues are one of the smallest, commonest and longest-present butterfly species around here in Maryland. Last year, they were flying in September and this spring I started seeing them towards the end of April. I photographed these butterflies about a week ago. According to Glassberg (Butterflies Through Binoculars, the East), in warm weather they breed continuously. The pictures of a mating pair that I photographed last September are here.

These butterflies are in a group called the blues (family Lycaenidae, subfamily Polyommatinae). The famous novelist Vladimir Nabokov (1899-1977) was also an accomplished lepidopterist and for a while worked at Harvard University's Museum of Comparative Zoology. He specialized in the family Lycaenidae.

11 May 2006

Two important archaeological meetings take place in Turkey every year. They are known as the Kazı Sonuçları Toplantısı (Excavation Results Meeting) and the Araştırma Sonuçları Toplantısı (Survey Results Meeting). During these meetings, archaeologists present usually preliminary results of the digs, surveys or other investigations they conducted in Turkey during the previous year. These reports are then published within a year or so and, in many cases and for many years, they become the only available published information for many of the excavations.

The reports for the 26th Excavation Results Meeting and the 22nd Survey Results Meeting, both of which took place in 2004, were published in 2005 and are now available freely here. The page is in Turkish. Each report consists of 2 volumes (cilt). If you click on the link for the volume you want to download, you will go to a new page where you have to click on a new link to start downloading the pdf file (all of which are quite large).

Most reports are in Turkish, but there are quite a number in English, German and French. One of the interesting articles that I read in the 26th Excavation Results Meeting was the work Briese & Pedersen did in Halikarnassos (Halicarnassus) to locate the remains of the palace of Maussollos (Mausolus), the king who married his sister.

10 May 2006

An ongoing exhibition thru 14 May at the National Gallery of Art in Washington D.C., presents an excellent, at the same time overloaded, introduction to the dadaist movement of the early 20th century. It took me an hour to go thru it and by the time I had come to the Cologne room (the exhibition was arranged by the major metropolitan centers of dadaism), I was already overwhelmed by all I was trying to absorb and started skipping the artworks and yet there was still New York and Paris to visit.

Dada originated in Zurich in 1916 as an artistic reaction against World War I. It quickly spread to other European cities, as well as to New York. Dadaists' general disdain for traditional arts and "masterpieces" was best exemplified in the dadaist Marcel Duchamp's L.H.O.O.Q.

What little I knew about Dada before I went to this exhibition had somewhat prejudiced my expectations in a negative direction. So it was a nice surprise to see many pleasing pieces that actually looked familiar. It was obvious that despite the short lifespan of Dada (it was over by about the early 1920s), it has since been a source of inspiration (and imitation) for many artists.

"Dada questioned and affected what art can look like, as well as what art can do, and set the stage for many avant-garde movements—including surrealism, pop art, and performance art. Dada also irrevocably changed the landscape of popular culture, influencing graphic design, advertising, and film, and breaking down barriers between high and low art."

09 May 2006

In most gastropods (snails and slugs) all openings of the body (except the pores of some mucus glands) are located in or near the head. Especially in slugs, the pneumostome (breathing pore), genital opening, anus and the opening of the kidney are very close to each other and only a short distance away from the mouth.

In terrestrial pulmonate gastropods the eggs are expelled thru the genital opening, which is located on the right side of the head (if the individual is dextral, otherwise, on the left side). The series of pictures below show the slug Arion subfuscus expelling one egg.

The developmental process that brings the pneumostome, anus and the opening of the kidney to the front of the body is known as torsion. Torsion, which occurs early in larval development, is defined as the twisting of the body behind the head, including the visceral mass, mantle and mantle cavity, 180° counterclockwise.

07 May 2006

Over at Abnormal Interests, Duane claims abnormally that he has the real Mona Lisa on the wall of his living room. Well, I've got news for him. I was down at D.C. today and I saw the Mona Lisa, facial hair and all, hanging outside the entrance of the National Gallery of Art. Now, that's gotta be the real one...

This huge reproduction of Marcel Duchamp's L.H.O.O.Q. is currently hanging outside the East Building of the National Gallery of Art in conjuction with the ongoing exhibition Dada. The original, which is in the exhibition, is barely larger than a postcard.

06 May 2006

As one expects from its name, Mike's Hard Lemonade appears to be lemonade with 5.2% alcohol. Although the label declares it to be a "malt beverage", I could not discern any malt flavor at all. It has a nice lemony aroma and the sweetness is just right. Overall, it is a pretty good drink. Keep this one definitely out of reach of children.

The company has a website, but as is usually the case with most brewers' websites, I couldn't find any useful information in it.

05 May 2006

Marissa-Cat, whose dealings with a chipmunk I storied here, caught a shrew in the backyard today. By the time I got the camera, she had put the shrew down and started playing with it.

The play session lasted a while, probably too long for the hapless shrew, but too short for Marissa-Cat. Finally, the shrew slid under some empty mulch bags and I took the opportunity to grab Marissa-Cat and bring her inside. It was enough excitement for one morning.

I noticed that the shrew had a slight gash on its back (barely visible underneath the grass blade over its back), but it wasn't bleeding and it was still quite active. Hopefully, it will recover.

04 May 2006

Among the more than 30 extant animal phyla, only 7 have evolved truly terrestrial representatives. Little1 proposed the following definition for a "truly terrestrial" animal: “If animals are effectively covered by a layer of water, then they are living as aquatic animals. If they are not so covered, which often means that they are bigger, as earthworms are usually bigger than soil-dwelling nematodes, then they can be said to be a truly terrestrial.” Provisionally and solely for the purpose of this post, I am defining a "truly terrestrial" animal as an animal that spends its entire lifespan on land and whose viability doesn't require it to be in a volume of water much larger than its own volume. This definition includes certain animals, such as slugs, that are almost always covered by a film of water whose volume is much smaller than the animals’ body volume, but excludes unfairly many insects (for example, dragonflies), many amphibians and snails that have aquatic larvae and terrestrial adults, but the phyla they are in are already in the list.

I am leaving out tardigrades (Tardigrada) and bdelloid rotifers (Rotifera), because, although some of their species live in mosses, lichens and in the soil and can survive desiccation much better than almost all truly terrestrial animals, they require to be surrounded with relatively large volumes of water to be active. Some nematode species (Nematoda) may be active outside of water at very high humidities, and thus, may also be considered truly terrestrial. But, I don’t know enough about the natural history of such species to confidently include them in my list.

I have mentioned this list here before, but back then I had forgotten to include onychophorans. Onychophorans are large, carnivorous, multi-legged, worm-like creatures that live in the forests of South America, Africa, South East Asia, Australia and New Zealand. Some authors consider them to be a subphylum of the Arthropoda.

03 May 2006

These land snails are among the mollusk denizens of the yards around my house. They usually hide under the rocks, but one summer we had more than a hundred of them aestivating on our garage door.

The taxonomy of the species in the genus Cochlicopa has long been a source of confusion and controversy. The exact number of Cochlicopa species in Europe depends on whose opinion one accepts. Giusti & Manganelli1 reported the results of their study of about 500 specimens of Cochlicopa from one location in Italy that showed that "Without signs of discontinuity, the specimens pass from individuals of the type C. nitens, through intermediate forms and C. lubrica and C. repentina-like forms to C. lubricella types. While the shell form changes, the genital tract details remain remarkably constant." One source of this phenotypic variability may be that these snails seem to be able to reproduce without mating thru selfing or parthenogenesis, thus creating different strains. Georg Armbruster has also been studying the European species and a short summary of his views are here.

I am tentatively identifying my snails as Cochlicopa lubrica. They are small snails with shells about 5 mm long. I will probably post about them again in the future.

1. Giusti, F. & G. Manganelli. 1992. The problem of the species in malacology after clear evidence of the limits of morphological systematics. Proceedings of the 9th International Malacological Congress, Gittenberger & Goud (eds.). pp. 153-172.

02 May 2006

Yesterday I went to a seminar at the University of Maryland by James Mallet (University College, London), who studies speciation in butterflies. I had read some of Dr. Mallet’s papers on species definitions and speciation, so this was a great opportunity to listen to him in person.

Dr. Mallet's seminar was about the speciation processes in Heliconius butterflies of South America and whether or not these butterflies speciate in allopatry or sympatry. These butterflies display Müllerian mimicry and there are many polymorphic races differing in wing color patterns. The races also hybridize and create hybrid zones. The predatory birds are more likely to go after the hybrids with rare color forms, because they are less likely to recognize them as toxic (frequency dependent selection). This results in the hybrid zones being narrow (~10-30 km wide). Furthermore, the hybrid zones shift spatially. In other words, one race seems to displace another.

The classical explanation of the presence of such polymorphic species is that during the last ice ages the South American rainforests were assumed to have been fragmented and the species to have evolved in allopatry in the remaining forest refugia before the gaps were reforested. But according to Dr. Mallet, recent pollen analyses indicate that the rainforests were never fragmented. He instead thinks that the current species distribution patterns were due to parapatric mechanisms in a continuous forest. In parapatric speciation, the new species evolve in contiguous populations initially with slight genetic differences.

All of this was presented in one hour. It was indeed a fast-paced, information-packed seminar. I enjoyed it. I was hoping to meet Dr. Mallet personally after the seminar, but I had to leave immediately due to a meeting I had elsewhere.

Dr. Mallet started and ended his talk with a picture of the Bank of England's £10 Charles Darwin note. Based on his interpretation of some statements in the Origin of Species, Dr. Mallet thinks Darwin may have favored a sympatric speciation process. If I can track down the relevant pages from the Origin, I will post them here.